Acid related disorders are numerous and often require chronic treatment and maintenance. Many of these diseases are without symptoms and therefore difficult to diagnose and treat. Gastric analysis is the quantitative measurement of gastric acid output and is a critical tool for the diagnosis of acid related disorders and the ongoing assessment of therapy response. At present gastric analysis requires a technically difficult procedure, using gastric aspiration through a nasogastric tube, that is costly, invasive, and uncomfortable for patients. Recently there is introduction of the SmartPill, which is a disposable pill that measures pH, temperature, and pressure throughout the GI tract. We have recently demonstrated that the SmartPill method of gastric acid analysis is a non-invasive, accurate and reproducible method for the quantitative measurement of gastric acid output in healthy subjects. We are presently in the second phase of the protocol studying patients with known acid related disorders to assess the utility of the SmartPill in characterizing and treating patients with gastric acid related disorders. Interested subjects will report to the NIH outpatient gastrointestinal clinic for evaluation. Subjects will have gastric analysis just before their next dose of anti-secretory medication using the gastric aspirate method followed by the SmartPill method. Outcomes will include a quantitative measurement of gastric acid output in unit time in patients with acid related disorders, and the assessment of acid suppression in patients treated with a variety of anti-secretory medications.